The invention relates to human lymphocyte-associated cell surface proteins.
Genes exclusively expressed by one cell lineage, but not by others, often define the function of that cell population. The generation of genes by the assembly of functionally independent domains has occurred frequently as new genes have evolved to encode proteins with new functions. An inducible endothelial-leukocyte adhesion molecule (ELAM-1) is expressed on the surface of cytokine-treated endothelial cells. This molecule is thought to be responsible for the accumulation of blood leukocytes at sites of inflammation by mediating the adhesion of cells to the vascular lining (Bevilacqua et al., Proc. Natl. Acad. Sci. USA 84:9238 (1987)). A granule membrane protein found in platelets and endothelial cells, termed GMP-140, has been cloned and is homologous with ELAM-1 (Johnston et al., Blood Suppl. 172:327A (1988)).
The invention generally features human lymphocyte-associated cell surface protein LAM-1, which includes domains homologous with binding domains of animal lectins, growth factors, and C3/C4 binding proteins; and the cDNA sequence encoding the LAM-1 protein or an immunogenic fragment of LAM-1. In a preferred embodiment, the cDNA sequence is isolated from a population of B cell-specific cDNAs from a human tonsil CDNA library, and the amino acid sequence of the protein is substantially as indicated in FIG. 2, more preferably 80% homologous with the sequence shown in FIG. 2 and most preferably 90% homologous. (Here xe2x80x9csubstantially as indicatedxe2x80x9d defines a sequence close enough to the indicated sequence to have the same function.)
In another aspect, the invention features antibody developed against lymphocyte-associated cell surface protein LAM-1, or a fragment thereof, or against a molecule that specifically associates with LAM-1, or a fragment thereof, to generate a functional molecule.
In another aspect, the invention features a method of identifying cells that express LAM-1 which involves reacting the antibody just described with a population of cells and isolating those that bind the antibody. Binding of antibody can also be used to block the receptor activity of LAM-1.
In another aspect, the invention features a method of treating a human patient suffering from a lymphocyte-mobilizing condition which involves administering a therapeutic amount of anantagonist to LAM-1 in a non-toxic pharmaceutical carrier substance. In preferred embodiments of the method the patient is suffering from tissue damage, an autoimmune disorder, or cancer, or the patient is an organ or tissue transplant recipient.
In another aspect, the invention features using the CDNA sequence defined above to isolate cross-hybridizing human DNAs.
In another aspect the invention features using LAM-1 to identify a ligand which will bind to it or to a molecule that is specifically associated with LAM-1 to generate a functional molecule.
As used herein the term antagonist includes any agent which interacts with LAM-1 and interfers with its function, eg., antibody reactive with LAM-1 or any ligand which binds to LAM-1.
Lymphocyte-associated cell surface protein LAM-1 is a unique receptor protein which has not previously been identified. LAM-1 contains domains that are homologous with those found in several different receptors and is a newly described member of a gene family that includes ELAM-1 and GMP-140, proteins which have been implicated in cell adhesion. LAM-1 most likely serves a similar function but is uniquely expressed by lymphocytes. The isolation of cDNA encoding LAM-1 has allowed the determination of the structure of this molecule; the cDNA has been used to transfer expression of LAM-1 to cells that do not express this gene.
Antibodies reactive with LAM-1 can be used to identify cells that express this receptor and to block its function. In addition, the CDNA protein product can be used to develop antagonistic ligands that can interfere with lymphocyte adhesion and function and thereby be used to treat such conditions as tissue damage and metastasis of cancer cells.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof and from the claims.
In the drawings
FIG. 1A shows a restriction map of the LAM-1 cDNA clone.
FIG. 1B shows a schematic model of the LAM-1 mRNA.
FIGS. 2A-2C show the determined cDNA nucleotide sequence and the deduced amino acid sequence of LAM-1.
FIG. 3A shows the homology of LAM-1 amino acid residues 35-160 with other proteins.
FIG. 3B shows the homology of LAM-1 amino acid residues 173-205 with other proteins.
FIG. 3C shows the homology of LAM-1 amino acid residues 207-268 with other proteins.